Remove documentation in kafka_consumer for metric_buffer

plugins/inputs/kafka_consumer/README.md

@@ -19,13 +19,10 @@ from the same topic in parallel.
   zookeeper_chroot = ""
   ## the name of the consumer group
   consumer_group = "telegraf_metrics_consumers"
-  ## Maximum number of metrics to buffer between collection intervals
-  metric_buffer = 100000
   ## Offset (must be either "oldest" or "newest")
   offset = "oldest"
 
   ## Data format to consume.
-
   ## Each data format has its own unique set of configuration options, read
   ## more about them here:
   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md